Amorphorization

Goal

To generate disordered, amorphous structures from crystalline inputs using molecular dynamics (MD). This is achieved through a "melt-quench" protocol, where the material is heated above its melting point and then rapidly cooled to "freeze" the liquid-like disorder.

Protocol: Melt-Quench

The standard Computational amorphization protocol involves:

1. Supercell Setup: The system must be large enough to avoid spurious periodicity effects in the amorphous state. Generally, $>100$ atoms is recommended.
2. Melting (Stage A): Heat the system to $T_{melt}$. $T_{melt}$ should be significantly higher than the experimental melting point (often 1000K higher) to ensure rapid loss of crystalline memory within MD timescales.
3. Equilibration (Stage A/B): Maintain the liquid at $T_{melt}$ for several picoseconds to ensure structural randomized.
4. Quenching (Stage B): Cool the system linearly to the target temperature (e.g., 300K).
   • Cooling Rate: A critical parameter. Typical MD cooling rates are $1-10$ K/ps ($10^{12}-10^{13}$ K/s). Slower rates yield more stable, realistic amorphous structures but are computationally expensive.
5. Annealing/Equilibration (Stage C): Relax the density and local structure at the target temperature.
6. Quenched/Static Relaxation (Stage D): Perform a final geometry optimization (0K) to find the local energy minimum of the amorphous state.

Instructions